University of Oulu

Xiangrui Kong, Martin J. Wolf, Michael Roesch, Erik S. Thomson, Thorsten Bartels-Rausch, Peter A. Alpert, Markus Ammann, Nønne L. Prisle & Daniel J. Cziczo (2018) Acontinuous flow diffusion chamber study of sea salt particles acting as cloud nuclei: deliquescence and ice nucleation, Tellus B: Chemical and Physical Meteorology, 70:1, 1463806, DOI: 10.1080/16000889.2018.1463806

A continuous flow diffusion chamber study of sea salt particles acting as cloud nuclei : deliquescence and ice nucleation

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Author: Kong, Xiangrui1,2; Wolf, Martin J.1; Roesch, Michael1;
Organizations: 1Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
2Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden
3Laboratory of Environmental Chemistry, Paul Scherrer Institute, Villigen, Switzerland
4Nano and Molecular Systems Research Unit, University of Oulu, Oulu, Finland
5Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.4 MB)
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Language: English
Published: Informa, 2018
Publish Date: 2018-06-13


Phase changes of sea salt particles alter their physical and chemical properties, which is significant for Earth’s chemistry and energy budget. In this study, a continuous flow diffusion chamber is used to investigate deliquescence, homogeneous and heterogeneous ice nucleation between 242 K and 215 K, of four salts: pure NaCl, pure MgCl₂, synthetic sea water salt, and salt distilled from sampled sea water. Anhydrous particles, aqueous droplets and ice particles were discriminated using a polarisation-sensitive optical particle counter coupled with a machine learning analysis technique. The measured onset deliquescence relative humidities agree with previous studies, where sea water salts deliquescence at lower humidities than pure NaCl. Deliquesced salt droplets homogenously freeze when the relative humidity reaches a sufficiently high value at temperatures below 233 K. From 224 K and below, deposition nucleation freezing on a fraction of NaCl particles was observed at humidities lower than the deliquescence relative humidity. At these low temperatures, otherwise unactivated salt particles deliquesced at the expected deliquescence point, followed by homogeneous freezing at temperatures as low as 215 K. Thus, the observed sea salt particles exhibit a triad of temperature-dependent behaviours. First, they act as cloud condensation particles (CCNs) > 233 K, second they can be homogeneous freezing nuclei (HFNs) < 233 K and finally they act as ice nucleating particles (INPs) for heterogeneous nucleation <224 K.

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Series: Tellus. Series B, Chemical and physical meteorology
ISSN: 0280-6509
ISSN-E: 1600-0889
ISSN-L: 0280-6509
Volume: 70
Issue: 1
Article number: 1463806
DOI: 10.1080/16000889.2018.1463806
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
116 Chemical sciences
1171 Geosciences
Funding: This work was supported by the National Science Foundation (AGS-1461305 & AGS-1461347) and the Swedish Foundation for International Cooperation in Research and Higher Education (IB2016-6612). XK and ET thank the Swedish Research Council VR and ET the Swedish Research Council Formas for support. XK for the VR International Postdoctoral fellowship (#2014-6924). MA and TBR appreciate support by the Swiss National Science Foundation (grant numbers 169176 and 149629). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No 717022).
EU Grant Number: (717022) SURFACE - The unexplored world of aerosol surfaces and their impacts.
Copyright information: © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.